Yes, but I think that will just lead to the same problem. Essentially that is what SQLite is doing for me already.
What is happening is that the high priority user interface thread is waiting for the low priority worker thread to complete its transaction. This effectively is reducing the priority of the user interface which either times out or becomes sluggish... In the busy handler can you find out what thread has the lock? If so, I could probably temporarily increase the priority of the locking thread and speed up the transaction processing/unlocking... Thanks again, -- BP << www.planet-hood.com >> Welcome to our world << > -----Original Message----- > From: John Stanton [mailto:[EMAIL PROTECTED] > Sent: Friday, December 16, 2005 1:07 PM > To: sqlite-users@sqlite.org > Subject: Re: [sqlite] Threads and locking > > Have you thought of using a lock to synchronise access to the > databaseso that only one thread at a time could change the > database although both could read simultaneously? > JS > > Barry Paul wrote: > > > > Hi, I am having some unexpected locking issues with SQLite. > > > > I have a desktop application that uses SQLite. The > application has a > > low priority worker thread that is constantly > > analyzing/adding/updating/deleting > > records in the database. The main application thread mainly > reads from > > the database but also does some updating/deleting. Both > threads have > > their own SQLite connection. > > > > My problem is that when I do updates in the main > application thread I > > quite often fail with a return value of SQLITE_BUSY. I have messed > > around with busy_timeouts and busy_handlers without much > success. My > > current busy handler (culled either from this list or the web) is: > > > > int busyHandler(void *pArg1, int iPriorCalls) { > > > > // sleep if handler has been called less than > threshold value > > if (iPriorCalls < 20) > > { > > // adding a random value here greatly > reduces locking > > if (pArg1 < 0) > > Sleep((rand() % 500) + 400); > > else Sleep(500); > > return 1; > > } > > > > // have sqlite3_exec immediately return SQLITE_BUSY > > return 0; > > } > > > > If I increase the transaction size on the low priority thread I get > > more update failures on the main thread. > > > > My schema is fairly simple and my tables contain < 90,000 rows. It > > would seem to me that with just two threads and this busy handler I > > should never (or very rarely) get SQLITE_BUSY. > > > > My theory is that the main application thread is getting locked out > > because it is waiting for the low priority thread to > release the lock > > on the database. Meanwhile something else is happing on the > machine at > > a higher priority and not letting the low priority thread > back in to > > finish the transaction and release the lock. > > > > Does this sound reasonable and is there a good way of dealing with > > this situation? Should I try to increase the priority of the > > background thread when I get a lock? Or is there some way > to make sure > > that transactions in the low priority thread are executed > all at once without interruption? > > > > Thanks for your time, > > > > -- > > BP > > << www.planet-hood.com >> Welcome to our world << > > > > > > >
